This is a stumper for me. Hopefully one of you guys will have an idea to help me out.

As best as we can figure here is the problem. SMTP emails over a certain size disappear from inbox once outlook is opened in cached mode.

We use Exch 2003 and Outlook 2010.
The issue began this morning. Users began complaining of not being able to receive their scans. We noticed that when we send a scan we can receive it in OWA and on ActiveSync phones, but as soon as we open Outlook they disappear. If we turn off cache mode they stay in the inbox and all is well. As we were pursuing this we noticed that Outlook also got rid of emails with voicemail attachments. Upon further investigation we discovered that small emails from the scanner and voicemail system don't disappear.

We then tested emails from mapi clients with large attachments, these work fine. It seems to be emails sent via smtp that disappear and then only larger attachments (not sure how large, but if they are under 1MB they don't disappear and again only when cache mode is turned on.

We use VIPRE. We did have email checking enabled. I turn this off and we still seemed to have the issue. We tested sending SMTP emails from addresses outside the organization and we are still having the same issue.

So the emails are delivered, but they just disappear. We couldn't find any rules that would be getting rid of them, and it works if cache mode is turned off.